1. Field of the Invention
The present invention relates to a method for manufacturing a laminated iron core (a rotor-laminated iron core or a stator-laminated iron core) having multiple punched holes in its circumferential direction, using a motor.
2. Description of the Related Art
Recently, as disclosed in JP-A-2008-42967, there has been spread a motor using a rotor structured such that its rotor-laminated iron core having an axial hole in its center includes multiple magnet-insert holes in which corresponding permanent magnets are inserted and respectively resin-sealed.
However, when closed magnet-insert holes are formed in the rotor-laminated iron core, magnetic flux directed toward the front and back of permanent magnets forms a magnetic path in the outer peripheral portion of the magnet-insert holes, thereby reducing the magnetic efficiency of the rotor. Thus, as shown in (A) to (C) of FIG. 7, there is proposed a method in which a bridge portion 71 formed between the end and outer periphery of a magnet-insert hole 70 of an iron core piece 72 forming a rotor-laminated iron core is plastically deformed by pressing to make the thickness of the plastic-deformed portion thinner than those of the remaining portions, thereby preventing an increase in torque variations, reducing the leakage magnetic flux and thus improving the efficiency of the motor (see JP-A-2006-50821). Here, FIG. 7 shows an axial hole 73, a punch 74, a die 75 and a scrap piece 76.
Patent Literature 1: JP-A-2008-42967
Patent Literature 2: JP-A-2006-50821